Process for improving the efficacy of oils used as binding agents and core sands forfoundry



United States Patent 2,903,796 Patented July 25, 1961 2,993,796 PROCESS FOR IMPROVING THE EFFICACY F 'OILS USED AS BINDING AGENTS AND CORE SANDS FOR FOUNDRY Lon Frangois Nicolas Schmit, 183 Ave. Milcamps, and Karl Paul Joseph Cassart, 52 Ave. du Roi Soldat, both of Brussels, Belgium N0 Drawing. Filed Oct. 26, 1959, Ser. No. 848,494 Claims priority, application Belgium Jan. 19, 1959 2 Claims. (Cl. 106-385) The present invention relates to a process for improving to an appreciable degree the binding power of drying oils, semi-drying oils and non-drying oils having single, double or treble bonds, which are used as binding agents in foundry work, especially for the manufacture of sand and zircon cores and molds for foundry purposes.

It is known that accelerators, and especially peroxides and chlorites (sodium chlorite), have been proposed for increasing the eflicacy of such binding agents (British Patent 801,931).

The use of such accelerators is, however, subject to certain disadvantages. Thus, they are unstable and for this reason they are subject to the loss of oxygen (the active factor) during storage. Moreover, their efiicacy depends on the ambient conditions, such as humidity and temperature. Furthermore, more especially as regards the chlorites, they are dangerous to handle and attack textiles and other organic materials with which they may come into contact, because of their corrosive nature. For this reason, they lower to some extent the quality of the oils used as binding agents.

It is an object of the present invention to obviate these disadvantages without impairing the efiicacy of the oil used as binding agent, and the invention resides in the use as accelerator of lead dioxide (formula: O=Pb=O), which is also known as lead peroxide. The lead dioxide is advantageously incorporated in the oil or other binding agent employed in an amount of from 0.3 to thereof.

The following examples further illustrate the invention:

Example 1 50 g. of lead dioxide are intimately mixed in a mixer with 100 kg. of siliceous sand at the ambient temperature; the binder is then added, this being for example 1.8 liters of a China-wood oil previously treated with 0.15% of cobalt and 0.45% of lead in the form of their naphthenates.

A core made with this mixture will have a resistance to compression of 750 g./cm. after 16 minutes.

Because of the small quantity of accelerator (PbO which is required, it is preferable from the point of view of ease of handling in the foundry to use the accelerator in admixture with a dry inert material, such as powdered silica or zirconium sand, in a proportion of from to of the inert material to 10 to 30% of the lead dioxide.

Experience has, however, shown'that in the present case, the inert material can with advantage be replaced wholly or in part by quick-lime (CaO).

The use of CaO has the advantage of guaranteeing a clear initiation of the setting while green or drying of the bonded sand, especially when the work is carried out in a cold humid atmosphere.

Example 2 A composition comprising 30 g. of PbO 30 g. of dry inert material (for example zirconium sand) and 30 g. of CaO are intimately mixed in a mixer with kg. of sand at ambient temperature. The binder (1.8 liters of the same one as employed in Example 1) is then added. The results obtained are similar to those obtained in Example 1.

What we claim is:

1. Sand core for foundry work containing a sand selected from the group consisting of powdered silica and zirconium sand and having admixed therewith a binding agent consisting of drying oil and, as a setting accelerator, lead dioxide in a quantity from about 0.3 to 10% by weight of said drying oil.

2. A process for improving the efficacy of drying oils used as binding agents for producing sand cores for foundry work which consists of incorporating lead dioxide as a setting accelerator for the binding agent, the lead dioxide being used in a proportion of from 0.3 to 10% by weight of the binding agent.

References Cited in the file of this patent UNITED STATES PATENTS 1,308,524 Hamelius July 1, 1919 2,556,335 Moser June 12, 1951 FOREIGN PATENTS 785,726 Great Britain Nov. 6, 1957 

1. SEND CORE FOR FOUNDRY WORK CONTAINING A SAND SELECTED FROM THE GROUP CONSISTING OF POWDERED SILICA AND ZIRCONIUM SAND AND HAVING ADMIXED THEREWITH A BINDING AGENT CONSISTING OF DRYING OIL AND, AS A SETTING ACCELERATOR, LEAD DIOXIDE IN A QUANTITY FROM ABOUT 0.3 TO 10% BY WEIGHT OF SAID DRYING OIL. 